Field of the Invention
The present invention relates to a pneumatic tire used for vehicles, particularly, in applications that require frequent starting, stopping, and turning operations.
Background Art
Pneumatic tires (hereinafter, simply referred to as “tires”) having various pattern structures have been proposed. For example, pattern structures disclosed in the following literatures can be mentioned.
The tire disclosed in JP S63-134312 A has a configuration in which a shallow and narrow connecting groove is provided between adjacent main grooves, and sipes are formed at the bottom of the connecting groove.
The tire disclosed in JP H11-048717 A has a configuration in which an island portion is formed by connecting two blocks.
The tires disclosed in JP 2002-029221 A and JP 2003-252009 A have a configuration in which a groove extending in the circumferential direction and a groove extending in the width direction are provided on a land area, and sipes are formed at the bottoms of the grooves.
Here, there are vehicles used in applications that require frequent starting, stopping, and turning operations on general roads (not roads between cities where high-speed running is assumed, but general roads in urban areas), such as a garbage truck. There is a demand for tires mounted on such a vehicle to reduce uneven wear and cracks in their ribs, while exerting a tractive force.
The tire disclosed in JP S63-134312 A has sipes formed in all the connecting grooves, and therefore the rigidity of blocks partitioned by the connecting grooves becomes insufficient when used as tires mounted on the vehicle in applications that require frequent starting, stopping, and turning operations on general roads. Therefore, uneven wear and cracks in the blocks may occur, which is not preferable.
Further, the tire disclosed in JP H11-048717 A has blocks that are independent from each other, and therefore the blocks easily move due to an external force. Therefore, when such tires are mounted on a vehicle used in applications that require frequent starting, stopping, and turning operations on general roads, cracks in the blocks and uneven wear in shoulder parts may possibly occur.
Further, the tires disclosed in JP 2002-029221 A and JP 2003-252009 A have all columns composed of blocks. Therefore, in the case where the blocks move due to an external force, there is no support portion. Accordingly, when such tires are mounted on a vehicle used in applications that require frequent starting, stopping, and turning operations on general roads, cracks in the blocks and uneven wear, particularly, in shoulder parts may possibly occur.